Rotary dryer

ABSTRACT

An improved rotary dryer having radially extended flights generally near the material feed end of the dryer, and a dam assembly having a movable ring segment rotatable between a dam position, wherein the movable ring segment extends in a direction transverse to the general direction of material flow through the dryer, and a flight position, wherein the movable ring segment extends in a direction aligned with the general direction of material flow through the dryer.

United States Patent [191 Fales Dec. 25, 1973 ROTARY DRYER Howard S. Fales, West Redding, Conn.

[75] Inventor:

[73] Assignee: Continental Oil Company, Ponca City, Okla.

22 Filed: Apr. 3, 1972 211 Appl. 310.; 240,630

[52] 11.8. CI 34/136, 432/108, 432/118 [51] F26b 17/18 [58] Field of Search 34/135, 136, 137;

[56] References Cited UNITED STATES PATENTS 3,026,627 3/1962 Moklebust 432/118 2,675,629 4/1954 Fisher 34/135 2,617,529 11/1952 McGehee 34/136 2,809,024 10/1957 Simon et a1 432/118 2,578,166 12/1951 Bill 34/136 2,470,315 5/1949 34/136 166,906 8/1875 Taggart 198/216 Primary Examiner-William F. ODea Assistant Examiner-Paul Devinsky Attorney-Joseph C. Kotarski et al.

[ 5 7 ABSTRACT An improved rotary dryer having radially extended flights generally near the material feed end of the dryer, and a dam assembly having a movable ring segment rotatable between a dam position, wherein the movable ring segment extends in a direction transverse to the general direction of material flow through the dryer, and a flight position, wherein the movable ring segment extends in a direction aligned with the general direction of material flow through the dryer.

8 Claims, 11 Drawing Figures PATENTEIJ 1512251975 SHEHIUFZ QQ E g 1 ROTARY DRYER BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to improvements in material dryers and, more particularly, but not by way of limitation, to an improved rotary dryer having extended radial flights and a dam assembly.

2. Brief Description of the Prior Art In the past there have been various devices proposed to facilitate the removal of moisture from granular-like materials wherein a drying medium was brought into intimate contact with the material to be dried. Some of the drying apparatus structures of this general type typically included a cylindrically shaped structure through which the material to be dried and the drying medium were simultaneously moved, wherein a portion of the structure was shaped to move the material through the dryer in a manner tending to increase the material-todrying medium contacting and, in general, improve the drying efficiency of the dryer.

One particular drying apparatus constructed in the past included a rotary drum rotatably supported for rotation about a horizontal axis, having a plurality of Iongitudinally extending flights or vanes and spaced discs for agitating the materials to be dried, maintaining a turbulence in the material flow and providing a tortuous path for the material and the drying medium moving through the dryer. The discs were generally ringshaped and the radial depth of the vanes was increased toward the material discharge end of the dryer.

One other rotary dryer of this general type was supported such that the angular inclination of the entire dryer could be altered to adjust the flow rate of the material through the dryer. This particular dryer included straight, angular and rectangular flights, and a smaller diameter inlet section having flights of increased length and closer spacing.

A rotary cooler construction, proposed in the past, had a ring dam assembly constructed of a plurality of segments wherein the radial height of a particular ring dam assembly was somewhat controlled by the number of segments utilized to construct particular ring dam assembly. The U.S. Pat., No. 2,840,922, issued to Erisman, disclosed a ring dam assembly of the type generally described above, and the U.S. Pat., Nos. 2,783,548, issued to l-Ialldorsson, and 2,578,166, issued to Bill, described a rotary dryer construction of the type generally mentioned before.

SUMMARY OF THE INVENTION The present invention contemplates an improved rotary dryer constructed for drying granular-like material having internal longitudinally extending flights wherein the flights generally near the material feed end of the rotary dryer have an increased radial length and one or more dam assemblies, each dam assembly having one or more movable ring segments rotatably supported within the dryer for rotation between a dam position,-

terial residence time and, in general, control the material flow through the dryer to provide improved dryer production rates, an improved drying efficiency, and to facilitate the removal of the material from the dryer during a clean-out phase of dryer operation.

An object of the invention is to provide a rotary dryer having improved production rates.

Another object of the invention is to provide a rotary dryer having an improved material-to-drying medium contacting through the dryer.

One other object of the invention is to provide a rotary dryer having an adjustable dam assembly for controlling the flow of material through the dryer in a faster, more efficient and more economical manner.

Yet another object of the invention is to provide a rotary dryer having an adjustably controlled material residence time.

A further object of the invention is to provide a r0- tary dryer dam assembly constructed to facilitate the removal of material from the dryer during a clean-out phase of the dryer operation in a more efficient, more economical and faster manner.

Another object of the invention is to provide a rotary dryer having an improved drying efficiency.

A still further object of the invention is to provide an improved rotary dryer which is more economical in construction and operation.

Other objects and advantages of the invention will be evident from the following detailed description when read in conjunction with the accompanying drawings which illustrate one embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side-elevational view of a rotary dryer constructed in accordance with the present invention having an upper portion thereof partially cut-away.

FIG. 2 is an end-elevational view of a typical baffle utilized in the rotary dryer of FIG. 1.

FIG. 3 is a sectional view showing the flight assembly construction and orientation in a portion of the rotary dryer of FIG. 1.

FIG. 4 is a sectional view, similar to FIG. 3, but showing the flight assembly construction and orientation in another portion of the rotary dryer of FIG. 1.

FIG. 5 is a sectional view, similar to FIG. 3, but showing yet another flight assembly construction and orientation in yet another portion of the rotary dryer of FIG.

FIG. 6 is a sectional view, similar to FIG. 3, but showing the flight assembly construction and orientation in still another portion of the rotary dryer of FIG. 1.

FIG. 7 is a sectional view, similar to FIG. 3, but showing the flight assembly construction and orientation in one other portion of the rotary dryer of FIG. 1.

FIG. 8 is an enlarged, elevational view diagrammatically showing a typical ring member portion and the dam assembly utilized in the rotary dryer of FIG. 1.

FIG. 9 is an enlarged, top plan view showing one of the movable ring segments and a portion of the turning assembly connected thereto of the rotary dryer of FIG. 1, and showing a portion of some of the rotary dryer flight assemblies.

FIG. 10 is an enlarged, partially sectionally, partially elevational view, taken substantially along the lines 10-10 of FIG. 9, and showing one of the movable ring segments in the dam position thereof.

FIG. 11 is a partial sectional, partial elevational view, similar to FIG. 10, but showing one of the movable ring segments in a flight position thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings in general, and to FIG. 1 in particular, shown therein and designated by the general reference numeral is a rotary dryer having a generally tubularly shaped shell 12 which is supported for rotation about a horizontal axis via a pair of conventional trunnions 14 and tires 16, the shell 12 being rotated by a motor drive 18 having a pinion gear 20 gearingly and drivingly connected to a ring gear 22 connected about the outer periphery of the shell 12. Rotary dryers which are supported for rotation about a horizontal axis, in a manner generally described before, are well-known in the art and a detailed description of the construction and the operation of the supports and the drive assembly is not required herein.

The shell 12 has a substantially enclosed material feed end 24 and a material discharge end portion 26, and a hollow portion is formed axially therethrough providing an inner peripheral surface 28 within the shell 12. A portion of the shell 12, generally near the material discharge end 26, has a taperingly reduced diameter for generally increasing the velocity of the drying medium to facilitate the removal of the dried material during the operation of the rotary dryer 10.

As shown in FIG. 1, one end of a transition section 30 is secured to the material feed end 24 of the rotary dryer 10, the opposite end of the transition section 30 being connected to a drying medium source (not shown) such as a heated air or gas supply or the like. The transition section 30, in one form, includes a plurality of filter elements (not shown) and, in general, provides a conduit for receiving, filtering and directing the drying medium into the material feed end 24 of the shell 12.

A material receiving chute 32 is disposed generally near the material feed end 24 of the shell 12, having a portion (shown in dashed-lines) in communication with the hollow portion of the shell 12. The material receiving chute 32 is constructed to receive the material to be dried and to discharge the material within the hollow portion of the shell 12, generally near the material feed end 24 thereof.

The rotary dryer 10 includes flight assemblies 34, baffle assemblies 36 and dam assemblies 38, each assembly being generally supported within the hollow portion of the shell 12 directing the flow of the received, moisture-laden material and drying medium through the rotary dryer 10 to substantially assure a predetermined moisture content in the dried material discharge from the material discharge end 26 of the outer shell 12.

In general, during the operation of the rotary dryer 10, the material to be dried is discharged into the hollow portion of the shell 12 via the material receiving chute 32 and the drying medium is introduced into the hollow portion of the shell 12 via the transition section 30, the shell 12 being rotated in a general direction 40 via the motor drive I8. The material and the drying medium move through the rotary dryer 10 in a general direction 42, generally from the material feed end 24 toward the material discharge end 26, the direction 42 being referred to herein as the general direction of material flow through the dryer" for the purpose of orientation. The flight assemblies 34, the baffle assemblies 36 and the dam assemblies 38 are each spaced and oriented with the shell 12 to direct the material and the drying medium within shell 12 in a manner substantially assuring a controlled, predetermined moisture removal, during the operation of the rotary dryer 10, in a manner to be described in greater detail below.

It should be noted that, although the rotary dryer 10 is described herein as being of the type generally referred to in the art as a direct-fired" type of dryer wherein the drying medium is preheated to a predetermined temperature level and subsequently fed directly into the dryer, the present invention can also be utilized in cooperation with an indirect-fired" type of dryer wherein heated conduits are disposed within or about the shell 12 heating the surrounding air and material within the hollow portion of the shell 12 to effect the required moisture removal from the material being processed through the dryer. The term drying medium is thus used herein to encompass and denote directfired and indirect-fired types of dryer constructions, and, in general, to encompass and denote a medium, such as air or the like, for example, utilized within the rotary dryer 10 to effect the moisture removal from the material being processed therethrough.

The rotary dryer 10 is, more particularly, constructed to receive and remove a predetermined amount of moisture from a granular-like material, such as polyvinylchloride resins (commonly referred to in the art by the letters PVC) which, in one form, are produced utilizing a process generally referred to in the art as the suspension process wherein the PVC resins are suspended in a fluid during one portion of the process, for example. In one particular application, the PVC resins are initially processed through a continuous centrifuge effecting an intiial moisture removal, and the PVC resins are subsequently fed through the rotary dryer, the dried PVC resins discharged from the rotary dryer being then processed through a dust collector wherein the drying medium is exhausted to atmosphere and the dried PVC resins are screened for particle size and further processed in a manner depending upon the particular process requirements, for example.

As shown in FIG. 1, the baffle assemblies 36, more particularly, include three longitudinally spaced baffles 44 supported within the hollow portion of the shell 12. As shown more clearly in FIG. 2, each baffle 44 includes a plurality of spaced openings 46, and four circumferentially spaced support arms 48, each support arm 48 being secured to the inner peripheral surface 28 of the shell 12 and to the outer periphery of the baffle 44 for centrally supporting the baffle 44 within the shell 12.

The flight assemblies 34, more particularly, include a plurality of flight assemblies 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72 and 74, each flight assembly 50 through 74 having a portion secured to the inner peripheral surface 28 of the shell 12 and extending generally radially inwardly therefrom. Each flight assembly 50 through 74, inclusive, also defines what is sometimes referred to below as a drying phase of the rotary dryer 10.

The flight assemblies 52 and 54 are constructed similarly, each flight assembly 52 and 54 comprising a plurality of longitudinally extending straight flight members 76, as shown in FIGS. 1 and 3 (only a portion of the straight flight members 76 being designated by a reference numeral in FIG. 3). Each straight flight member 76 also extends a distance from the inner peripheral surface 28 radially inwardly toward the axial center line of the shell 12, the radially inwardly extension of the flight members 76 being greater than the radially inwardly extension of the other fight members of the other flight assemblies, for reasons to be made more apparent below.

The straight flight members 76 are circumferentially spaced about the inner peripheral surface 28 of the shell 12, thereby providing a longitudinally extending material bed space 77 generally between pairs of the straight flight members 76 (only some of the bed spaces 77 being designated by a reference numeral in FIG. 3). The material is generally retained within some of the bed spaces 77 and subsequently showered therefrom as the shell 12 is rotated during the operation of the rotary dryer 10, in a manner well-known in the art.

The flight assemblies 56 and 58 are also each similarly constructed, and each flight assembly includes a plurality of longitudinally extending straight flight members 78 and a plurality of longitudinally extending angular flight members 80, the straight flight members 78 and the angular flight members 80 being alternated in sequence and circumferentially spaced about the inner peripheral surface 28 of the shell 12 to provide a longitudinally extending material bed space 82 therebetween, as shown in FIG. 4 (only some of the flight members 78 and 80 and some of the bed spaces 82 being designated by a reference numeral in FIG. 4). The angular flight members 80 include a radially extending portion and outer end portion which is angularly oriented with respect to the straight, radially extending portion thereof. 7

The flight assemblies 60 and 62 are each constructed similarly and, as shown more clearly in FIG. 5, each flight assembly 60 and 62 includes a plurality of the angular flight members 80 circumferentially spaced about the peripheral surface 28 of the shell 12 to provide a longitudinally extending material bed space 84 generally between each pair of the angular flight members 80 (only some of the flight members 80 and some of the bed spaces 84 being designated in FIG. 5).

The flight assemblies 64 and 66 are each constructed similarly, and, as shown in FIG. 6, each flight assembly 64 and 66 includes a plurality of the angular flight members 80 and a plurality of longitudinally extending L-shaped flight members 86, the angular flight members 80 and the L-shaped flight members 86 being alternated in sequence and circumferentially spaced about the inner peripheral surface 28 of the shell 12 to provide a longitudinally extending material bed space 88 therebetween (only some of the flight members 80 and 86 and some of the bed spaces 88 being designated in FIG. 6 by a reference numeral). Each L-shaped flight member 86 includes a radially extending portion having the outer most end portion thereof formed at a right angle with respect to the radially extending portion thereof.

The flight assemblies 68, 70 and 72 are each constructed similarly and, as shown in FIG. 7, each flight assembly 68, 70 and 72 includes a plurality of the L- shaped flight members 86 circumferentially spaced about the inner peripheral surface 28 of the shell 12 to provide longitudinally extending material bed spaces 90 generally between each pair of the L-shaped flight members 86 (only some of the flight members 86 and some of the bed spaces 90being designated by a reference numeral in FIG. 7).

In one form, the flight assembly 50, generally near the material feed end 24 of the rotary dryer 10, includes a plurality of radially extending straight flight members shaped and oriented to provide an overall spiral shaped flight (not shown) for facilitating the moving of the received material generally toward the dryer phase defined by the flight assemblies 52 and 54. In one form, the flight assembly 74, generally near the material discharge end 26 of the rotary dryer 10, includes a plurality of striaght flight members 76 shaped to provide a conically shaped array of flight members leading toward the discharge opening formed through the material discharge end 26 of the rotary dryer 10 (not shown).

During the operation of the rotary dryer 10, the material to be dried is disposed generally within some of the material bed spaces 77, 82, 88 and 90, when the bed spaces are disposed generally near the lower portions of the shell 12, and the material held by the flight members 76, 78, 80 and 86 is moved generally toward the upper portions of the shell l2,'as the shell 12 is rotated in a general direction 40. The material retained within the material bed spaces 77, 82, 88 and 90 is released or dropped therefrom and showered downwardly when the material bed spaces 77, 82, 88 and 90 haee been rotated through a sufficient number of degrees toward the upper portion of the rotary dryer 10. The angled flight members 80 and the L-shaped flight members 86 are shaped to retain portions of the material within the bed spaces formed thereby through a greater rotation of the shell 12 to enhance the materialto-drying medium contacting within the rotary dryer 10, in a manner well-known in the art.

As mentioned before, the straight flight members 76 of the second and the third dryer phase, defined by the flight assemblies 52 and 54, each extend a greater distance radially inwardly as compared with the inwardly extension of the flight members 78, 80 and 86 in the other dryer phases. The additional radial extension of the straight flight members 76 at these initial dryer phases has been found to substantially increase the drying efficiency and the production rate of the rotary dryer 10.

The dam assemblies 38, more particularly, include three axially spaced clams 94 disposed and supported generally within the hollow portion of the shell 12, each dam 94 extending generally transversely across a portion of the shell 12. Each dam 94 includes a ring member 96, as shown more clearly in FIG. 8, having an outer periphery 98 disposed generally near the inner peripheral surface 28 of the shell 12, and an opening 100 formed through a central portion thereof forming an inner periphery 102. Each ring member 96 includes at least one arc-shaped movable ring segment 104, having an outer periphery 106, an inner periphery 108 and opposite sides and 112, the ring member 94, as shown in FIG. 8, more particularly, including a plurality of movable ring segments 104, for reasons to be made more apparent below.

Each movable ring segment 104 is shaped such that, in an assembled position, the outer peripheries 106 of each of the movable ring segments 104 cooperate to form a portion of the outer periphery 98 of the ring member 96, and the inner peripheries 108 of each of the movable ring segments 104 cooperate to form the inner periphery 102 of the ring member 96. The sides 1 l and l 12 of each of the movable ring segments 104, in a preferred form, are each formed along a line radially extending from the center of the ring member 96, each of the movable ring segments 104 thereby cooperating to form a segmental portion of the ring member 96, in one position of the movable ring segments 104.

As shown in FIG. 8, the ring member 96 also includes a stationary ring segment 114 having an outer periphery substantially corresponding to the outer periphery 98 of the ring member 94 and an inner periphery substantially corresponding to the inner periphery 102 of the ring member 94, the stationary ring member 114 being secured to the inner peripheral surface 28 of the shell 12 generally about the outer periphery thereof, and extending generally radially inwardly therefrom, in an assembled position of each dam 94. The movable ring segments 104 and the stationary ring segment 114, more particularly, cooperate to form the ring member 96 of each dam 94 for reasons to be described in greater detail below.

As shown more clearly in FIGS. 9, and 11, each movable ring segment 104 has a circumferential length 116 and a radial height 118, the circumferential length 116 decreasing generally from the outer periphery 106 toward the inner periphery 108 of each movable ring segment 104. The radial height 118 of each movable ring segment 104 is slightly less than the radial height of the stationary ring segment 114 such that, in an assembled position of each of the movable ring segments 104, wherein the inner peripheries 108 thereof are arcuately aligned to form the inner periphery 100 of the ring member 96, a space 122 exists generally between the outer peripheries 106 and the adjacent portion of the inner peripheral surface 28 of the shell 12, as shown more clearly in FIG. 10. The circumferential length 116 is sized and each movable ring segment 104 is oriented within the shell 12 such that each movable ring segment 104 can be rotated between adjacent flight members to a position wherein each movable ring segment 104 lies in a plane substantially coplanar with the stationary ring segment 114 and to a position wherein each movable ring segment 104 lies in a plane extending generally transversely to the planar disposition of the stationary ring segment 114 or, in other words, between a dam position and a flight position, for reasons and in a manner to be described in greater detail below.

Each movable ring segment 104 is, more particularly,

' movably supported within the shell 12 via a turning assembly 124 such that each movable ring segment 104 is independently rotatable in a direction 126 to a flight position (shown in FIG. 11) wherein the movable ring segment 104 extends in a direction aligned with the general direction of material flow through the rotary dryer 10, and in a direction 128 to a dam position (shown in FIGS. 9 and 10) wherein the movable ring segment 104 extends in a direction transverse to the general direction of material flow through the rotary dryer 10. Each turning assembly 124 includes a cylindrically shaped shaft 130 having an upper end portion 132 extending through an opening 134 formed through the shell 12 and extending a distance radially beyond the inner peripheral surface 28 thereof, and a lower end portion 136 extending a distance radially from the outer periphery of the shell 12, as shown in FIGS. 9, 10 and ll.

A recess 138 is formed in the upper end portion 132 of the shaft providing a substantially flat segment receiving surface 140 extending a distance axially along a portion of the shaft 130 and a segment receiving land 142 extending transversely across a portion of the shaft 130, spaced a distance from the upper end thereof. A portion of the outer periphery 106 of each movable ring segment 104 is disposed on the segment receiving land 142 of one of the turning assemblies 124, and each movable ring segment 104 is secured to the shaft 130 of one of the turning assemblies 124 via fasteners 144 (only one of the turning assemblies 124 being shown in the drawings).

As shown in FIGS. 10 and 11, a bearing ring 146 is disposed about a portion of the shaft 130, the bearing ring 146 being generally disposed between the inner peripheral surface 28 of the shell 12 and the outer periphery 106 of the movable ring segment 104. The bearing ring 146 is thus disposed generally within a portion of the gap 122 and provides a bearing surface between the movable ring segment 104 and the shell 12 during the rotation of the movable ring segment 104 via the turning assembly 124.

A cylindrically shaped extension 150, having opposite ends and a shaft opening 152 formed therethrough, is secured to the outer periphery of the shell 12 and extends a distance radially therefrom. In the assembled position of the extension 150, the shaft opening 152 thereof is aligned with the opening 134 in the shell 12 and the shaft 130 extends through the shaft opening 152 and through the opening 134, as shown more clearly in FIGS. 10 and 11.

A portion of the shaft 130 extends through the opening 152 of the extension and through an opening formed in a cylindrically shaped base 156, the base 156 being secured to the portion of the shaft 130 extending through a portion thereof via a fastener 158. One end ofa square-shaped handle 160 is secured to one end of the base 156, and one end ofa lock extension 162 is secured to the opposite end of the base 156, the lock extension 162 extending a distance from the base 156 to a position wherein the end thereof, generally opposite the end secured to the base 156, is disposed generally near a portion of the outer periphery of the extension 150. A wing nut type of fastener 164 is threaded through an opening formed in a portion of the lock extension 162, one end of the fastener 164 engaging an adjacent portion of the outer periphery of the extension 150 to lockingly prevent rotation of the shaft 130, thereby securing the movable ring segment 104 in one rotated position in the locked position of the fastener 164.

A collar 166 is disposed about a portion of the shaft 130, the collar 166 being interposed generally between the extension 150 and the base 156, and an elastomeric seal member 168 is disposed about a portion of the shaft 130, the seal member 168 being generally disposed between the collar 166 and the extension 150. More particularly, a counterbore is formed in one end of the extension 150, and a portion of the elastomeric seal member 168 is disposed within the counterbore, as shown in FIG. 10. In an assemblied position of the turning assembly 124, the base 156 is secured to the lower end portion 136 of the shaft 130 and the movable ring member 104 is secured to the upper end portion 132 of the shaft 130 such that the collar 166 compressingly engages and secures the seal member 168 in a sealing position wherein the seal member 168 sealingly engages the shaft 130 and a portion of the shell 12 or, more particularly, a portion of the extension 150, forming a fluid seal therebetween.

It should be particularly noted that a number of movable ring segments 104 comprising approximately onehalf of the circumferential length of the ring member 96 and one stationary ring segment 114 comprising approximately one-half of the circumferential length of the ring member 96 have been shown in the drawings merely for the purpose of clarity of description. In one form, the stationary ring segment 114 is replaced entirely with movable ring segments 104 and, in one other form, the ring member 96 comprises an extended stationary ring segment 114 and fewer movable ring segments 104. The number of movable ring segments 104 in each dam 94 generally determines the area of the dam which can be adjustably varied by rotating the movable ring segments 104 via the turning assemblies 124 connected thereto. In general, the number of dams 94 and the number of movable ring segments 104 in a particular rotary dryer construction are varied depending upon a particular design or application requirement.

OPERATION OF FIGS. 1 THROUGH 11 The rotary dryer 10, described in detail before, receives the granular-like material via the material receiving chute 32 and receives the drying medium via the transition section 30, the material and the drying medium moving through the rotary dryer in a general direction 42 from the material feed end 24 toward the material discharge end 26 of the shell 12, and the dried material being discharged through an opening in the material discharge end 26 of the shell 12. The material and the drying medium are, more particularly, moved through each of the drying phases of the rotary dryer 10 (defined by the flight assemblies 50 through 74, inclusive), the material being continually picked-up by the flight assemblies 34 and subsequently showered downwardly to bring the material and the drying medium into intimate contact as the material and the drying medium are moved through the shell 12 .of the rotary dryer 10. A portion of the drying medium is generally passed through the openings 46 of the baffle assemblies 36 and the material is forced generally downwardly toward the inner peripheral surface 28 of shell 12 by the baffles 44 to further enhance the material-todrying medium contacting within the rotary dryer 10.

As mentioned before, the straight flight members 76 of the flight assemblies 52 and 54 each have an increased radial length and thus the material bed spaces 77 formed thereby have an increased volume capacity, as compared with the material bed spaces formed by the remaining flight assemblies of the rotary dryer 10. The received material processed through these intial dryer phases (the flight assemblies 52 and 54) has a greater moisture content with respect to the remaining downstream dryer phases and the increased radial length of the flight members disposed therein has been found to substantially increase the rotary dryer production rate (the amount of material processed per hour through the rotary dryer 10), is particularly with respect to a rotary dryer utilized to process PVC resins, generally mentioned before. In the dam position of each of the segments 104 of each dam 94, the dams 94 each contact a portion of the material being dried and generally impede the flow of the material in an axial direction 42 through the rotary dryer 10, and force the material into the adjacent material bed spaces, thereby substantially assuring all of the material processed via the rotary dryer 10 is showered via the flight assemblies immediately preceding each dam 94. In this manner, the material-to-drying medium contacting through the rotary dryer 10 is substantially increased in a manner substantially assuring that all of the material being discharged from the rotary dryer 10 has been intimately contacted by the drying medium, thereby hindering the progress of slugs of material through the rotary dryer 10. The dams 94 also hinder the flow of the material through the rotary dryer 10, as mentioned before, and thus provide an efficient and economical means for increasing the material residence time in the rotary dryer 10. The dams 94 thus cooperate with the radially extending straight flight members 76 to generally increase the production rate of the rotary dryer 10 via increasing the material residence time and increasing the material-to-drying medium contacting, thereby increasing the drying efficiency of the rotary dryer 10 in a manner substantially assuring a consistent moisture content in the discharged dried material. It should also be noted that the dams 94 operate to control the material bed depth.

As described before, in a preferred form, each dam 94 includes one or more movable ring segments 104 which can be rotated between a dam position and a flight position, thereby providing an adjustably controlled dam area which can be quickly, conveniently and economically adjusted to provide the optimum dam area within the rotary dryer 10 as determined by the particular rotary dryer construction and process requirements (the dam area being the area of each ring member 94 oriented in a plane generally transverse to the general direction of material flow through the rotary dryer 10).

It should also be noted that one or more of the movable ring segments 104 of each of the dams 94 can be rotated to various angular positions generally between the dam position and the flight position thereof via the turning assembly 124 connected thereto, thereby angularly orienting some of the movable ring segments 104 to induce an increased material turbulence generally at the dam 94 position, which may be desired in some applications. The movable ring segments 104 are locekd in the angularly extending positions, the dam position, and the flight position via the fastener 164 to prevent inadvertent rotation during the operation of the rotary dryer 10. Thus, since each of the movable ring segments 104 is rotatable between the dam position and the flight position via a turning assembly 124 located on the outer periphery of the dryer 10, the position of each segment 104 can be adjustably oriented without requiring a prolonged shut-down of the rotary dryer 10 and in a manner eliminating the necessity of having to disassemble any portion of the rotary dryer 10 to effect a change in the dam 94 orientation, thereby providing a permanently installed rotary dyrer dam construction and yet maintaining a flexibility with respect to the effect of each installed dam to meet various application and process requirements.

In one particular application utilizing a rotary dryer constructed similar to the rotary dryer 10; but, having a single dam 94 located generally between the flight assemblies 64 and 66, the darn being constructed of a single movable ring segment 104 and a single stationary ring segment 114, the rotary dryer was utilized in a process for producing PVC resins and its copolymers. In this particular application, the PVC resins were transferred in a slurry form to a continuous centrifuge providing an initial separation of the PVC resins and the moisture (the slurry form of the PVC resins entering the continuous centrifuge was comprised of approximately 70% water and 30% PVC resins; and the PVC resins discharged from the continuous centrifuge was comprised of approximately 80% PVC resins and water). The material from the centrifuge was processed through the rotary dryer, an air blower being connected to the material discharge end of the rotary dryer augmentingly pulling the material and the drying medium through the rotary dryer. In this particular application, the process required that the material discharged from the rotary dryer have a maximum moisture content of approximately 0.25 percent. Prior to radially extending the straight flight members of the flight assemblies 52 and 54 and installing the dam (described generally above), the moisture content of the material discharged from the rotary dryer was in excess of 1 percent, and the production rate was limited to approximately 5,500 pounds of PVC resins processed through the rotary dryer per hour. Utilizing the extended straight flight members in the flight assemblies 52 and 54 and the dam (described before), the moisture content of the PVC resins discharged from the rotary dryer was reduced to less than 0.25 percent and the production rate was increased to the extent that the rotary dryer was processing 7,000 pounds of PVC resins per hour. In this particular application, the full extent of the increased production rates achieved by the improved rotary dryer construction have not yet been realized, primarily due to limitations of the equipment downstream from the rotary dryer.

In rotary dryers having permanently and semipermanently installed baffles producing to some extent a damming effect within the rotary dryer, it has also been found that there is generally some build-up to material on the upstream side of baffles, thereby resulting in some difficulties encountered in attempting to remove the material from the rotary dryer during a cleaning-out phase of the operation. Utilizing the dam 94 of the present invention, one or more of the movable ring segments 104 are rotated to approximately the flight positions thereof, thereby effectively reducing the dam area and providing an opening through each of the dams 94 for the material to be passed. The movable ring segments [04 positioned in approximately the flight positions thereof act to facilitate the removal of the material build-up on the upstream side of the dams 94. In one form, one of the movable ring segments 104 can be partially rotated toward the flight position and secured in this position during the operation of the rotary dryer 10, the partially rotated movable ring segment 104 acting to continually reduce the possibility of material build-up behind the dams 94.

ln one form (not shown in the drawings), one or more dippers, constructed of a pair of scoop shaped elements slidably connected for variable depth control, are pivotally secured to portions of the ring member 96, each dipper cooperating to facilitate the removal of the material immediately upstream of each dam 94 and to substantially reduce the possibility of material stratification. in one other form (not shown in the drawings), the dippers are constructed and connected for pivotal movement about a pivotal axis substantially transverse to axial center line of the shell 12, thereby essentially providing a variable width dipper acting to further reduce the possibility of the build-up of material fines immediately upstream of the dam 94 and to substantially reduce the possibility of material stratification.

It should also be noted that the material temperature and moisture content varies as the material is moved through the shell 12 toward the material discharge end 26 of the rotary dryer 10. The dams 94, in one preferred embodiment, are longitudinally spaced in the shell 12 such that each dam 94 cooperates with the flight assemblies immediately upstream therefrom to control the material-to-drying medium contacting and the material residence time for each of the drying phases processing materials having substantially the same material and moisture content, this particular spacing of the dams 94 may be particularly desirable in processing temperature sensitive material. The term moisture is used herein to denote various forms such as water, solvent or the like.

Changes can be made in the construction and the operation of the embodiment of the invention described herein without departing from the spirit and the scope of the invention as defined in the following claims.

What is claimed is:

1. A rotary dryer receiving a drying medium and material for reducing the moisture content of a material as the material moves through the rotary dryer, comprising:

a shell having a material feed end, a material discharge end and a hollow portion extending therethrough forming an inner peripheral surface;

means receiving the material to be dried within the hollow portion of the shell generally near the material receiving end;

means receiving the drying medium within the hollow portion of the shell; and

dam means supported within the hollow portion of the shell having a portion movable between a dam position, wherein the movable portion extends in a direction transverse to the general direction of the material flow through the shell, and a flight position, wherein the movable portion extends in a direction aligned with the general direction of the material flow through the shell; and

at least one dam disposed within the hollow portion of the shell, each dam comprising: a ring member having an outer periphery disposed generally near the inner periphery surface of the shell and an opening through a central portion thereof forming an inner periphery; and

the ring member is defined further to include:

an arc-shaped stationary ring segment, having an inner periphery and an outer periphery, the outer periphery secured to a portion of the inner peripheral surface of the shell;

an arc-shaped movable ring segment, having an inner periphery and an outer periphery and opposite ends, movable between the darn position and the flight position, the movable ring segment disposed in a plane substantially coplanar with the stationary ring segment in the dam position thereof and disposed in a plane generally transverse to the planar disposition of the stationary ring segment in the flight position thereof, the outer peripheries of the movable ring segment and the stationary ring segment forming the outer periphery of the ring member in the dam position of the movable ring segment, and the inner peripheries of the stationary ring segment and the movable ring segment forming the inner periphery of the ring member in the dam position of the movable ring segment; and turning means connected to the movable ring segment for rotating the movable ring segment between the dam position and the flight position.

2. The rotary dryer of claim 1 wherein the turning means is defined further to include: a shaft, having an upper end portion extending through the shell and a lower end portion extending outwardly beyond the shell, the upper end portion connected to the movable ring member; means connected to the lower end portion of the shnaft for rotating the movable ring segment connected thereto between the dam position and the flight position; and seal means sealingly engaging the shaft and a portion of the shell forming a seal therebetween.

3. The rotary dryer of claim 2 wherein the movable ring member is movable supported within the shell and a clearance gap exists generally between the outer periphery of the movable ring member and the inner peripheral surface of the shell; and wherein the means for rotating the movable ring member is defined further to include: bearing means interposed generally between the outer periphery of the movable ring member and the inner peripheral surface of the shell.

4. The rotary dryer of claim 2 wherein the turning means includes: means to secure the shaft in predetermined rotated positions thereby securing the movable ring member connected thereto in the darn position and the flight position.

5. The rotary dryer of claim 1 wherein the ring member includes a plurality of movable ring segments; and wherein the dam is defined further to include: turning means connected to each movable ring segment for independently rotating each movable ring segment between the dam position and the flight position.

6. The rotary dryer of clam l defined further to include: more than one dam supported within the hollow portion of the shell, the dam being longitudinally spaced in the shell.

7. The rotary dryer of claim 1 defined further to include: a plurality of circumferentially spaced flight member means, each flight member means secured to the inner peripheral surface of the shell; and wherein the movable ring segment is positioned and has a circumferential length for rotation generally between the flight member means generally adjacent thereto.

8. The rotary dryer of claim 1 defined further to include: a plurality of circumferentially spaced, longitudinally extending flight member means, the flight member means generally near the material receiving end of the shell extending a greater distance radially inwardly with respect to the radial inwardly extension of the remaining flight member means. 

1. A rotary dryer receiving a drying medium and material for reducing the moisture content of a material as the material moves through the rotary dryer, comprising: a shell having a material feed end, a material discharge end and a hollow portion extending therethrough forming an inner peripheral surface; means receiving the material to be dried within the hollow portion of the shell generally near the material receiving end; means receiving the drying medium within the hollow portion of the shell; and dam means supported within the hollow portion of the shell having a portion movable between a dam position, wherein the movable portion extends in a direction transverse to the general direction of the material flow through the shell, and a flight position, wherein the movable portion extends in a direction aligned with the general direction of the material flow through the shell; and at least one dam disposed within the hollow portion of the shell, each dam comprising: a ring member having an outer periphery disposed generally near the inner periphery surface of the shell and an opening through a central portion thereof forming an inner periphery; and the ring member is defined further to include: an arc-shaped stationary ring segment, having an inner periphery and an outer periphery, the outer periphery secured to a portion of the inner peripheral surface of the shell; an arc-shaped movable ring segment, having an inner periphery and an outer periphery and opposite ends, movable between the dam position and the flight position, the movable ring segment disposed in a plane substantially coplanar with the stationary ring segment in the dam position thereof and disposed in a plane generally transverse to the planar disposition of the stationary ring segment in the flight position thereof, the outer peripheries of the movable ring segment and the stationary ring segment forming the outer periphery of the ring member in the dam position of the movable ring segment, and the inner peripheries of the stationary ring segment and the movable ring segment forming the inner periphery of the ring member in the dam position of the movable ring segment; and turning means connected to the movable ring segment for rotating the movable ring segment between the dam position and the flight position.
 2. The rotary dryer of claim 1 wherein the turning means is defined further to include: a shaft, having an upper end portion extending through the shell and a lower end portion extending outwardly beyond the shell, the upper end portion connected to the movable ring member; means connected to the lower end portion of the shaft for rotating the movable ring segment connected thereto between the dam position and the flight position; and seal means sealingly engaging the shaft and a portion of the shell forming a seal therebetween.
 3. The rotary dryer of claim 2 wherein the movable ring member is movably supported within the shell and a clearance gap exists generally between the outer periphery of the movable ring member and the inner peripheral surface of the shell; and wherein the means for rotating the movable ring member is defined further to include: bearing means interposed generally between the outer periphery of the movable ring member and the inner peripheral surface of the shell.
 4. The rotary dryer of claim 2 wherein the turning means includes: means to secure the shaft in predetermined rotated positions thereby securing the movable ring member connected thereto in the dam pOsition and the flight position.
 5. The rotary dryer of claim 1 wherein the ring member includes a plurality of movable ring segments; and wherein the dam is defined further to include: turning means connected to each movable ring segment for independently rotating each movable ring segment between the dam position and the flight position.
 6. The rotary dryer of claim 1 defined further to include: more than one dam supported within the hollow portion of the shell, the dam being longitudinally spaced in the shell.
 7. The rotary dryer of claim 1 defined further to include: a plurality of circumferentially spaced flight member means, each flight member means secured to the inner peripheral surface of the shell; and wherein the movable ring segment is positioned and has a circumferential length for rotation generally between the flight member means generally adjacent thereto.
 8. The rotary dryer of claim 1 defined further to include: a plurality of circumferentially spaced, longitudinally extending flight member means, the flight member means generally near the material receiving end of the shell extending a greater distance radially inwardly with respect to the radial inwardly extension of the remaining flight member means. 